[TUN] Add a missing dependency on enabling the crc32 libraries

Patch by Steve French <smfltc@us.ibm.com>
Signed-off-by: Max Krasnyansky <maxk@qualcomm.com>

drivers/net/Kconfig

@@ -84,6 +84,7 @@ config EQUALIZER
 config TUN
 	tristate "Universal TUN/TAP device driver support"
 	depends on NETDEVICES
+	select CRC32
 	---help---
 	  TUN/TAP provides packet reception and transmission for user space
 	  programs.  It can be viewed as a simple Point-to-Point or Ethernet